如题所述
第1个回答 2012-04-10
20以内的加减法:
进位:(1+19,2+18,....9+11),(9+9,9+8,9+7,...9+1),(8+8,8+7,...8+2),(7+7,7+6,....7+3),........5+5.
推位:20-19,20-18,...20-1),(18-9,17-9,17-8,16-9,16-8,16-7,.....,11-8,....11-2
进位:(1+19,2+18,....9+11),(9+9,9+8,9+7,...9+1),(8+8,8+7,...8+2),(7+7,7+6,....7+3),........5+5.
推位:20-19,20-18,...20-1),(18-9,17-9,17-8,16-9,16-8,16-7,.....,11-8,....11-2
第2个回答 2012-04-12
20以内的加减法:
进位:(1+19,2+18,....9+11),(9+9,9+8,9+7,...9+1),(8+8,8+7,...8+2),(7+7,7+6,....7+3),........5+5.
推位:20-19,20-18,...20-1),(18-9,17-9,17-8,16-9,16-8,16-7,.....,11-8,....11-2
的问题可能比别人差,只要让提问采纳被采纳没关系,虽然我回答者明白就行!
进位:(1+19,2+18,....9+11),(9+9,9+8,9+7,...9+1),(8+8,8+7,...8+2),(7+7,7+6,....7+3),........5+5.
推位:20-19,20-18,...20-1),(18-9,17-9,17-8,16-9,16-8,16-7,.....,11-8,....11-2
的问题可能比别人差,只要让提问采纳被采纳没关系,虽然我回答者明白就行!
第3个回答 2012-04-12
逢10必进位,十位不够减就退位